System and method for precooling in hydrogen or helium liquefaction processing

ABSTRACT

Described herein are systems and processes for precooling hydrogen or helium gas streams for liquefaction using liquid nitrogen having reduced energy consumption and amount of liquid nitrogen usage. The systems include a stream of pressurized liquid nitrogen, at least one turboexpander, and at least one heat exchanger.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority benefit under 35 U.S.C. §119(e) to U.S. Provisional Application No. 63/207,684, filed Mar. 15, 2021, the contents of which is incorporated by reference herein in its entirety.

FIELD OF THE DISCLOSURE

This disclosure relates to a precooling process using liquid nitrogen in hydrogen or helium liquefaction. More specifically, the disclosure relates to a method of precooling hydrogen or helium gas using a process based on a supply of liquid nitrogen, incorporating at least one turboexpander and one or more heat exchangers, together which reduce the amount of nitrogen required for precooling and reduce the energy consumed in the precooling process.

BACKGROUND OF THE DISCLOSURE

Liquefaction of hydrogen and helium requires a large expenditure of energy. Hydrogen has the second lowest boiling point of all substances, with a boiling temperature of −253° C. at atmospheric pressure. Only helium has a lower boiling point. The liquefaction process is divided into several stages, such as: hydrogen compression, pre-cooling, and liquefaction. In the pre-cooling stage of hydrogen liquefaction, the hydrogen gas may be cooled from ambient temperature to approximately −191° C. Large scale hydrogen liquefiers utilize liquid nitrogen supplied from an associated nitrogen/air liquefaction plant. Processes for the liquefaction of hydrogen and helium frequently use liquid nitrogen for precooling purposes in the liquefaction process. The use of liquid nitrogen reduces the overall energy requirement for production of liquid hydrogen or liquid helium. In turn, the liquid nitrogen derived for this employment is produced separately with a substantial expenditure of energy. As a means for precooling hydrogen or helium prior to liquefaction, the direct evaporation of liquid nitrogen, which is conventionally supplied at low pressure and at a cold temperature for vaporization and superheating, entails large temperature differences between the hydrogen or helium warm fluids and the cold nitrogen fluid.

FIG. 5 is an example of the conventional precooling processing of hydrogen gas with liquid nitrogen (500). Liquid nitrogen (LIN) is supplied in a stream (504) and hydrogen gas (warm or at ambient temperature) is supplied in a stream (501). The liquid nitrogen stream (504) and the hydrogen gas stream (501) flow in countercurrent through a heat exchanger (502) resulting in a cooled hydrogen gas stream (503) and a warmed nitrogen gas stream (505). The condition of supplied liquid nitrogen is typical of that produced by cryogenic air separation plants.

The precooling process directly effects the total energy required for hydrogen or helium liquefaction. The energy required for precooling, as represented by the energy to produce the required liquid nitrogen, is a substantial part of the total energy to liquefy liquid hydrogen or helium. Recent work has concentrated on means to reduce the total energy required to liquefy hydrogen or helium by different means for supplying precooling refrigeration, and means for reduction of the liquid nitrogen requirement.

SUMMARY OF THE DISCLOSURE

A method for precooling hydrogen or helium gas prior to liquefaction using a liquid nitrogen stream is disclosed. That method includes: a.) providing a pressurized liquid nitrogen stream containing liquid nitrogen at a pressure between about 15 bar(a) and about 70 bar(a); b.) passing the pressurized liquid nitrogen stream and a partially-cooled hydrogen or helium gas stream through a first heat exchanger that exchanges heat between the pressurized liquid nitrogen stream and the partially-cooled hydrogen or helium gas stream to provide a first partially-warmed nitrogen stream and a precooled hydrogen or helium gas stream; c.) passing the first partially-warmed nitrogen stream through one or more turboexpanders that lowers the temperature and pressure of the partially-warmed nitrogen stream to provide a cold nitrogen stream; and d.) passing the cold nitrogen stream through the first heat exchanger and through a second heat exchanger to provide the precooled hydrogen or helium gas stream, and a fully-warmed nitrogen gas stream. Step (d) may include: passing the cold nitrogen stream through the first heat exchanger that exchanges heat between the cold nitrogen stream and the partially-cooled hydrogen or helium gas stream to provide a second partially-warmed nitrogen gas stream and the precooled hydrogen or helium gas stream; and passing the second partially-warmed nitrogen gas stream through the second heat exchanger that exchanges heat between the second partially-warmed nitrogen gas stream and a warm hydrogen or helium gas stream to provide a fully-warmed nitrogen gas stream and the partially-cooled hydrogen or helium gas stream. The first heat exchanger and the second heat exchanger may be separate devices, or two parts within a single heat exchanger. The method may further include applying an auxiliary refrigeration system coupled to the second heat exchanger.

Step (a) may include: supplying a liquid nitrogen stream produced at a saturation pressure of less than about 10 bar(a); followed by increasing the pressure of the liquid nitrogen stream to provide the pressurized liquid nitrogen stream. Step (a) may include: supplying a liquid nitrogen stream produced at a saturation pressure of less than about 10 bar(a); splitting the liquid nitrogen stream into a first portion of the liquid nitrogen stream and a second portion of the liquid nitrogen stream; and increasing a pressure of the first portion of the liquid nitrogen stream to provide the pressurized liquid nitrogen stream. The second portion of the liquid nitrogen stream may pass through the first heat exchanger to provide a third partially-warmed nitrogen stream. The third partially-warmed nitrogen stream may pass through the second heat exchanger to provide a second fully-warmed nitrogen gas stream. The pressurized liquid nitrogen has a pressure between about 15 bar(a) and about 70 bar(a), or about 20 bar(a) and about 55 bar(a).

The pressurized liquid nitrogen stream may be split into a first pressurized liquid nitrogen stream and a second pressurized liquid nitrogen stream, and the first pressurized liquid nitrogen stream and the second pressurized liquid nitrogen stream passed separately through the first heat exchanger to exchange heat between the first and the second pressurized liquid nitrogen streams and the partially-cooled hydrogen or helium gas stream.

Another method for precooling hydrogen or helium gas using a liquid nitrogen stream is disclosed that includes: a.) supplying a liquid nitrogen stream produced at a saturation pressure of less than about 10 bar(a); b.) directing a first portion of the liquid nitrogen stream to a first heat exchanger to provide a first partially-warmed nitrogen stream; c.) directing the first partially-warmed nitrogen stream to a second heat exchanger to provide a first fully-warmed nitrogen gas stream; c.) increasing a pressure of a second portion of the liquid nitrogen stream to provide a pressurized liquid nitrogen stream at a pressure between about 15 bar(a) and about 70 bar(a); d.) passing the pressurized liquid nitrogen stream and a partially-cooled hydrogen or helium gas stream through the first heat exchanger in countercurrent to provide a second partially-warmed nitrogen gas stream and a precooled hydrogen or helium gas stream; e.) passing the second partially-warmed nitrogen gas stream through the second heat exchanger that exchanges heat between the second partially-warmed nitrogen gas stream and a warm hydrogen or helium gas stream to provide a second fully-warmed nitrogen gas stream and the partially-cooled hydrogen or helium gas stream; f.) passing the second fully-warmed nitrogen gas stream through one or more turboexpanders that lower the temperature and pressure of the second fully-warmed nitrogen gas stream to provide a cold nitrogen stream; e.) passing the cold nitrogen stream through the first heat exchanger that exchanges heat between the cold nitrogen stream and the partially-cooled hydrogen or helium gas stream to provide a third partially-warmed nitrogen gas stream and the precooled hydrogen or helium gas stream; and f) passing the third partially-warmed nitrogen gas stream through the second heat exchanger that exchanges heat between the third partially-warmed nitrogen gas stream and a warm hydrogen or helium gas stream to provide a third fully-warmed warm nitrogen gas stream and the partially-cooled hydrogen or helium gas stream. Step (g) may include: routing the second fully-warmed nitrogen stream through one or more compressors and one or more coolers before passing the second fully-warmed nitrogen stream through the one or more turboexpanders. Step (g) may include: passing the second fully-warmed nitrogen stream through two turboexpanders connected in series. The method may further include applying an auxiliary refrigeration system coupled to the second heat exchanger.

The pressurized liquid nitrogen stream may be split into a first pressurized liquid nitrogen stream and a second pressurized liquid nitrogen stream; and the first pressurized liquid nitrogen stream and the second pressurized liquid nitrogen stream routed separately through the first heat exchanger, and optionally, the second heat exchanger.

The method may include a system of recooling the second or third fully-warmed nitrogen gas stream, the system of recooling comprising: i.) passing the second or third fully-warmed nitrogen gas stream through a first compressor and a first cooler to obtain a compressed and cooled nitrogen gas stream, wherein the first compressor is coupled to the second heat exchanger and to the first cooler; ii.) passing the compressed and cooled nitrogen gas stream through one or more turboexpanders; and iii). passing the turboexpanded nitrogen gas stream through the second heat exchanger to provide a fourth fully-warmed nitrogen gas stream. Step (ii) includes passing the compressed and cooled nitrogen gas stream through two turboexpanders connected in series.

A precooling system using liquid nitrogen for hydrogen or helium liquefaction is also disclosed. The system may include: a warm hydrogen or helium gas stream; a pressurized liquefied nitrogen stream from a supply of liquefied nitrogen; a heat exchanger; and at least one turboexpander coupled to the heat exchanger and configured to lower a temperature of a partially-warmed nitrogen gas stream discharged from the heat exchanger. The heat exchanger may be configured to exchange heat between the pressurized liquefied nitrogen stream and a warm hydrogen or helium gas stream to increase a temperature of the pressurized liquefied nitrogen stream and decrease a temperature of the warm hydrogen or helium gas stream to provide a precooled hydrogen or helium gas stream, and a warm nitrogen gas stream,. In another aspect, the system includes a first heat exchanger configured to exchange heat between the pressurized liquefied nitrogen stream and a partially-cooled hydrogen or helium gas stream to increase a temperature of the pressurized liquefied nitrogen stream to provide a partially-warmed nitrogen gas stream, and decrease a temperature of the partially-cooled hydrogen or helium gas stream; at least one turboexpander configured to lower the temperature of the partially-warmed nitrogen gas stream; and a second heat exchanger configured to exchange heat between the partially-warmed nitrogen gas stream and the warm hydrogen or helium gas stream to increase a temperature of the partially-warmed nitrogen gas stream to provide a fully-warmed nitrogen gas stream, and to decrease a temperature of the warm hydrogen or helium gas stream.

The system may also include at least one compressor and at least one cooler configured to receive the warm nitrogen gas stream discharged from the heat exchanger, at least one turboexpander configured to receive the warm nitrogen gas stream after passage through the at least one compressor and the at least one cooler, and/or optionally, a valve coupled to the turboexpander.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic diagram of a system to precool hydrogen gas using liquid nitrogen, a first and second heat exchanger, a turboexpander, and auxiliary refrigeration.

FIG. 2 is a schematic diagram of a system to precool hydrogen gas using liquid nitrogen, a first and second heat exchanger, a turboexpander, auxiliary refrigeration, and other components.

FIG. 3 is a schematic diagram of a system to precool hydrogen gas using liquid nitrogen, a first and second heat exchanger, multiple turboexpanders, multiple compressors, multiple coolers, auxiliary refrigeration, and other components.

FIG. 4 is a schematic diagram of a system to precool hydrogen gas using liquid nitrogen, a first and second heat exchanger, two turboexpanders, two compressors, two coolers, and other components.

FIG. 5 is a schematic diagram of a conventional system to precool hydrogen or helium gas using liquid nitrogen.

DETAILED DESCRIPTION

The processes disclosed herein have been developed, in part, to reduce the amount of liquid nitrogen required for precooling hydrogen or helium gas in the process of liquefaction. These processes and precooling systems employ additional steps and equipment to more fully utilize the amount of liquid nitrogen supplied into the precooling system. That is, the externally derived liquid nitrogen is consumed at a reduced rate compared to conventional precooling systems. It is also understood that where liquid nitrogen has also been used for precooling other hydrogen or helium streams employed in the liquefaction process (the so-called recycle streams), the means for reducing the liquid nitrogen consumption therein are also applicable.

In a method for precooling hydrogen or helium gas using a liquid nitrogen stream disclosed herein, a liquid nitrogen supply is pressurized and supplies most of its cooling capacity in heat exchange with the hydrogen or helium gas, which warms the nitrogen; the warmed nitrogen is then machine-expanded to a cold temperature and re-introduced for heat exchange with hydrogen or helium. In effect, the supplied liquid nitrogen is passed through the same heat exchanger a second time (in a loop), thus reducing the liquid nitrogen requirement and the attendant energy required for its own production. The energy costs to produce this reduced quantity of liquid nitrogen are thereby reduced. Since this cost is a significant component of the energy cost for producing liquid hydrogen or liquid helium, the overall cost of liquefaction is reduced, which is of commercial importance. The costs of precooling may be reduced by about 20% to about 50%.

The term “machine-expanded,” as used herein, includes any device utilized to produce work by reducing the enthalpy of the fluid expanded, such as a turboexpander or a reciprocating expansion engine.

Conventional liquid nitrogen precooling processes for hydrogen have a liquid nitrogen expenditure of about 7 to about 10 kg liquid nitrogen per kg liquefied hydrogen. The precooling process disclosed herein may have a liquid nitrogen expenditure of about 4 to about 6 kg liquid nitrogen per kg liquefied hydrogen, or about 4.30 to about 5.35 kg liquid nitrogen per kg liquefied hydrogen. This is a significant reduction in liquid nitrogen expenditure over the conventional process.

A method for precooling hydrogen or helium gas using a liquid nitrogen stream is disclosed, whereby an overall reduction of the amount of liquid nitrogen is used compared to conventional precooling.

That method includes providing a pressurized liquid nitrogen stream that may have a pressure of about 15 bar(a) to about 70 bar(a), about 20 bar(a) to about 60 bar(a), or 20 bar(a) to about 50 bar(a). The pressurized liquid nitrogen may have a temperature of about −147° C. to about −196° C., about −169° C. to about −195° C., or about −189° C. to about −194° C.

Pressurized liquid nitrogen may be supplied directly into the method disclosed herein. Alternatively liquid nitrogen may be supplied from an external source having a saturation pressure of about 1 bar(a) to about 10 bar(a), which may then be pressurized by any means known in the art. The liquid nitrogen may be pressurized by utilizing a pump or by compression to increase the pressure.

In an embodiment, the pressurized liquid nitrogen stream may be split into a first pressurized liquid nitrogen stream and a second pressurized liquid nitrogen stream, and each of the first pressurized liquid nitrogen stream and the second pressurized liquid nitrogen stream may be directed through a first heat exchanger to exchange heat between each of the first and second pressurized liquid nitrogen streams and the partially-cooled hydrogen or helium gas stream. The two partially-warmed nitrogen streams having passed separately through the first heat exchanger may be combined into one stream before being directed through at least one turboexpander.

In an embodiment, a liquid nitrogen stream produced at a saturation temperature at less than about 10 bar(a) is supplied into the system and split into a first portion of the liquid nitrogen stream and a second (or remaining) portion of the liquid nitrogen stream. The first portion of the liquid nitrogen stream may have the pressure increased by any means known in the art, e.g., by pump or compression, to provide a pressurized liquid nitrogen stream, and the second portion of the liquid nitrogen stream may be directed into the first heat exchanger, and then optionally into the second heat exchanger, separately from the routing of the pressurized liquid nitrogen stream.

A “pump” as used herein means a mechanical device to increase the pressure of a liquid.

A warm hydrogen or helium gas stream is supplied for precooling and may be supplied from one or more hydrogen or helium feed streams or cycle hydrogen or helium feed streams. The warm hydrogen gas stream may be produced from natural gas, electrolysis of water, or other chemical methods. A warm hydrogen or helium gas stream may be supplied from a source outside of the liquefaction process or it may be a recycle stream from elsewhere in the process. The warm hydrogen gas stream may be at any pressure suitable for its eventual liquefaction. The warm hydrogen gas stream may have a pressure between about 20 bar(a) and about 80 bar(a), or about 20 bar(a) and about 40 bar(a) and/or have a temperature of about 25° C. to about 35° C. The warm hydrogen gas stream may have a composition of about 75% ortho and about 25% para spin isomers.

Ortho-para conversion of the hydrogen gas may be incorporated as the hydrogen gas is cooled. Ortho-para conversion may occur in the first heat exchanger and in the second heat exchanger, with the passages of the heat exchanger(s) optionally packed with a catalyst for the feed hydrogen. The catalyst may be any known for use in the art for this purpose. This may improve the overall energy efficiency of the liquefaction process. The precooled hydrogen gas stream may have a temperature of about −173° C. to about −196° C., about −180° C. to about −196° C., or about −190° C. to about −192° C., and/or a pressure of about 15 bar(a) to about 100 bar(a), or about 20 bar(a) to about 80 bar(a). The precooled hydrogen gas stream may be about 53% ortho and about 47% para.

A “heat exchanger,” as used herein, means any device capable of transferring heat energy or cold energy from one medium to another medium, such as between at least two distinct fluids. Heat exchangers include “direct heat exchangers” and “indirect heat exchangers.” Thus, a heat exchanger may be of any suitable design, such as a co-current or counter-current heat exchanger, an indirect heat exchanger (e.g. a spiral wound heat exchanger or a plate-fin heat exchanger such as a brazed aluminum plate fin type), direct contact heat exchanger, shell-and-tube heat exchanger, spiral, hairpin, core, core-and-kettle, printed-circuit, double-pipe or any other type of known heat exchanger.

As used herein a first heat exchanger transfers energy between counter current streams in the colder steps of the process, while a second heat exchanger transfers energy between counter current streams in the warmer part of the process. The precooled hydrogen or helium gas stream exits from the first heat exchanger, while the fully-warmed nitrogen gas stream exits from the second heat exchanger. The first and second heat exchangers may be two parts of one heat exchanger, or they may be two separate heat exchangers. When the first and second heat exchangers are two parts of one heat exchanger, the heat exchanger includes multiple outputs for streams passing therethrough, including, but not limited to exit points for valves at different locations on the unit.

As used herein, the term “indirect heat exchange” means the bringing of two fluids into heat exchange relation without any physical contact or intermixing of the fluids with each other. Core-in-kettle heat exchangers and brazed aluminum plate-fin heat exchangers are examples of equipment that facilitate indirect heat exchange.

A next step includes passing the partially-warmed nitrogen stream through at least one turboexpander that lowers the temperature and pressure of the partially-warmed nitrogen stream to provide a cold nitrogen stream. The turboexpander may be coupled to the first heat exchanger by any means known in the art. The turboexpander exhaust may flow to the first heat exchanger. The turboexpander may include a brake, such as a blower, fan or an oil pump that circulates and cools, to dissipate energy. The turboexpander may be coupled to a compressor for capturing the energy generated by the turboexpander.

By passing through one turboexpander, the warm nitrogen stream may be cooled by about 30 degrees to about 130 degrees, or about 50 to about 100 degrees, and/or the pressure may be reduced by about 2 bar to about 100 bar, 4 bar to about 60 bar, or about 30 bar to about 50 bar. By passing the stream through a second turboexpander connected in series to the first turboexpander, the temperature and pressure of the stream may be further reduced. The first turboexpander may be coupled to the second turboexpander.

A “turboexpander” as used herein means any device employed to achieve a reduction in temperature by effecting a reduction in pressure, while generating useful energy which can be either removed from or captured to assist in the required cooling process by the performance of work, such as but not limited to, radial inward flow machines typically used in cryogenic processing. The turboexpander uses energy in an expanded gas to generate mechanical energy through a rotation. The turboexpander turns at high speed and then the energy may be transferred via a shaft to a compressor, which recovers the energy by compressing a separate feed gas stream. This process elevates the pressure feed gas stream to the compressor, enabling it to supply useful energy back into the system.

Optionally, the method includes passing the partially-warmed nitrogen stream through at least one compressor and at least one turboexpander, in any order, to provide a cold nitrogen stream that is routed back through the first heat exchanger or second heat exchanger. The method may include passing the partially-warmed nitrogen stream through two to five compressors and two to five turboexpanders to provide a cold nitrogen stream that is routed back through the first heat exchanger or second heat exchanger. The method may include passing the partially-warmed nitrogen stream through two to five compressors, two to five turboexpanders, and two to five coolers to provide a cold nitrogen stream that is routed back through the first heat exchanger. An equal number of coolers may be used in the process as the number of compressors. One or more of the turboexpanders may be connected by a shaft to one compressor.

A “cooler” as used herein means any water or air cooler known in the art that removes heat from the system, such as, a fin-fan unit for cooling process streams by ambient air, a shell-and-tube unit, or a plate cooler which uses a water or brine system for cooling process streams from elevated temperatures to near-ambient temperatures. Passing a stream through a cooler may lower the temperature of the stream by about 40° C. to about 100° C.

When passing the cold nitrogen stream through the first heat exchanger, this creates a loop in the process of precooling which is a second passage of the nitrogen stream though the first heat exchanger. This allows for the same originally supplied nitrogen to be recycled and used in countercurrent for cooling the hydrogen or helium gas stream a second time in the first heat exchanger. The cold nitrogen stream may be routed through a valve before passing through the first heat exchanger for the second time in the process of precooling. Turboexpanders have a limited range of pressure ratios (inlet pressure/outlet pressure), so a valve may be added to the system to further lower the pressure, for example, instead of adding a second turboexpander, if needed. Accordingly, when a valve is used, there is a pressure drop in the nitrogen stream across the valve. The valve may decrease the temperature and pressure, and increase the % gas in the nitrogen stream.

After passing through the second heat exchanger, the fully-warmed nitrogen gas stream may have a temperature of about 15° C. to about 30° C., or about 20° C. to about 28° C., and a pressure of about 0.5 bar(a) to about 2 bar(a), or about 1 bar(a) to about 2 bar(a). The fully-warmed nitrogen gas stream may be routed through another processing loop comprised of at least one turboexpander, and optionally at least one compressor, for pressurizing and cooling and then reintroduced into the second heat exchanger. The fully-warmed nitrogen gas stream may be routed through another processing loop comprised of at least one turboexpander, and optionally at least one compressor, for pressurizing and cooling and then reintroduced into the first heat exchanger and then into second heat exchanger.

Also disclosed is a precooling system using liquid nitrogen for hydrogen or helium liquefaction. The system may comprise: a warm hydrogen or helium gas stream; a pressurized liquefied nitrogen stream from a supply of liquefied nitrogen; a first heat exchanger configured to exchange heat between the pressurized liquefied nitrogen stream and a partially-cooled hydrogen or helium gas stream to increase a temperature of the pressurized liquefied nitrogen stream to provide a partially-warmed nitrogen gas stream, and decrease a temperature of the partially-cooled hydrogen or helium gas stream; at least one turboexpander configured to lower the temperature of the partially-warmed nitrogen gas stream; and a second heat exchanger configured to exchange heat between the partially-warmed nitrogen gas stream and the warm hydrogen or helium gas stream to increase a temperature of the partially-warmed nitrogen gas stream and decrease a temperature of the warm hydrogen or helium gas stream. The first heat exchanger or the second heat exchanger may be coupled to one turboexpander. The precooling system may comprise a valve coupled to one turboexpander. The valve may configured to reduce the pressure of the nitrogen gas stream.

The precooling system may comprise at least one compressor and at least one cooler, and optionally at least one turboexpander, configured to receive the fully-warmed nitrogen gas stream after passage through the second heat exchanger. The precooling system may comprise at least one turboexpander configured to receive the warm nitrogen gas stream after passage through the at least one compressor and the at least one cooler. The precooling system may comprise one to four compressors, one to four coolers, and one to four turboexpanders configured to receive the fully-warmed nitrogen gas stream after passage through the second heat exchanger, with each compressor being coupled to a cooler, and the one to four turboexpanders being connected after the compressors and coolers in the system.

Also disclosed is a precooling system using liquid nitrogen for hydrogen or helium liquefaction, the system comprising: a warm hydrogen or helium gas stream; a pressurized liquefied nitrogen stream from a supply of liquefied nitrogen; a heat exchanger configured to exchange heat between the pressurized liquefied nitrogen stream and a warm hydrogen or helium gas stream to increase a temperature of the pressurized liquefied nitrogen stream to provide a warm nitrogen gas stream, and decrease a temperature of the warm hydrogen or helium gas stream to provide a precooled hydrogen or helium gas stream; and at least one turboexpander coupled to the heat exchanger and configured to lower a temperature of a partially-warmed nitrogen gas stream discharged from the heat exchanger. The precooling system may also include at least one compressor and at least one cooler configured to receive the warm nitrogen gas stream after passage through the heat exchanger, and optionally, at least one turboexpander configured to receive the warm nitrogen gas stream after passage through the at least one compressor and the at least one cooler. The precooling system may also include a valve coupled to the turboexpander configured to reduce the pressure of the nitrogen gas stream.

Described herein are systems and processes relating to precooling hydrogen or helium gas using a liquid nitrogen stream. Specific embodiments of the disclosure include those set forth in the following paragraphs as described with reference to the Figures. While some features are described with particular reference to only one Figure (such as FIG. 1, 2, 3, 4), they may be equally applicable to the other Figures and may be used in combination with the other Figures or the foregoing discussion.

FIGS. 1-4 show non-limiting examples of various systems and processes 100, 200, 300, 400 for precooling hydrogen or helium gas using a liquid nitrogen stream according to this disclosure. A liquid nitrogen stream (LIN) 104, 204, 304, 404 is supplied from any LIN supply system, such as one or more tankers, tanks, pipelines, or any combination thereof. The systems include at least one heat exchanger, e.g., a first heat exchanger 131, 231, 331, 431 and a second heat exchanger 130, 230, 330, 430. These systems include a pump 132, 232, 332, 432 to receive the liquid nitrogen stream and increase the pressure to make a pressurized liquid nitrogen stream 105, 250, 306, 406. The pressurized liquid nitrogen stream may be split into more than one stream, e.g., two streams 250, 240. Warm hydrogen or helium gas is supplied from any source in a stream 101, 201, 301, 401 that is routed through the second heat exchanger to provide a partially-cooled hydrogen or helium gas stream 102, 202, 302, 402, which is routed through the first heat exchanger for further cooling to provide a precooled hydrogen or helium gas stream 103, 203, 303, 403.

FIG. 1 shows a system 100 for precooling hydrogen or helium gas using a liquid nitrogen stream. The liquid nitrogen stream 104 is directed through a pump 132 to increase the pressure. The pressurized liquid nitrogen stream 105 is routed through a first heat exchanger 131 in which energy is transferred between the partially-cooled hydrogen or helium gas stream 102 and the pressurized liquid nitrogen stream 105, which flow in countercurrent, thereby increasing the temperature of the nitrogen stream. The partially-warmed nitrogen gas stream 106 is then directed through a turboexpander 133 to provide a cold nitrogen gas stream 107 which has a lower pressure and lower temperature than stream 106. It will be envisioned that the system may include more than one turboexpander connected in series for reducing the temperature and pressure of the nitrogen stream before re-entry into the first heat exchanger. The disclosure includes alternate embodiments where, in each identified location of a turboexpander, multiple turboexpanders may be connected in series, such as two, three, or four, where needed to further reduce the pressure of the stream.

The cold nitrogen gas stream 107 is then routed through the first heat exchanger to complete the loop, and for a second pass of the nitrogen gas stream through the first heat exchanger, in which energy is transferred between the partially-cooled hydrogen or helium gas stream 102 and the cold nitrogen stream 107, to provide a partially-warmed nitrogen gas stream 108 and a precooled hydrogen or helium gas stream 103.

The partially-warmed nitrogen gas stream 108 is then routed through a second heat exchanger 130 in which energy is transferred between the warm hydrogen or helium gas stream 101 and the partially-warmed nitrogen gas stream 108, to provide a fully-warmed nitrogen gas stream 109 and a partially-cooled hydrogen or helium gas stream 102, which is then routed through the first heat exchanger 131.

The second heat exchanger 130 may include auxiliary refrigeration, here shown as propene streams 114, 115. Liquid propene stream 114 passes through the second heat exchanger which exchanges heat between the auxiliary refrigeration and the warm hydrogen or helium gas stream 101, and exits as a gas propene stream 115. The second heat exchanger may include auxiliary refrigeration coupled to the second heat exchanger. Auxiliary refrigeration supplements coolant in the precooling process and may be supplied from any other known sources of refrigeration. Auxiliary refrigeration may be a vapor compression refrigeration, absorption refrigeration, mixed refrigerant refrigeration, or any other means known to extract heat from the warm hydrogen or helium gas stream. Auxiliary refrigeration may comprise of one refrigeration stream, or two refrigeration streams, being the same or different. Auxiliary refrigeration may be a propene refrigeration stream which supplies a liquid stream at a temperature of about −20° C. to −50° C., and exits the system as a gas stream.

Having described an embodiment of the disclosure, additional aspects will now be described. FIG. 2 illustrates a system 200 for precooling hydrogen or helium gas using a liquid nitrogen stream. In FIG. 2, liquid nitrogen is pumped to an elevated pressure, and, after vaporizing and superheating for cooling hydrogen, passes through a turboexpander and returns to conduct additional cooling of the hydrogen. A valve 235 is shown between streams 208 and 209 for meeting the aerodynamic limitations of the turboexpander, if needed. Auxiliary refrigeration is provided at a temperature level much warmer than that of liquid nitrogen as part of the cooling process, for instance, from propene vapor-compression refrigeration.

The system of FIG. 2 is configured so that the split pressurized liquid nitrogen streams 240, 250 are routed through the first heat exchanger 231, whereby the split pressurized liquid nitrogen streams 240, 250 are warmed and the pressure remains substantially constant, e.g., any pressure differential may be less than about 1 bar(a). Each of the split partially-warmed nitrogen streams 241, 251 exits the first heat exchanger at a different output, though it will be envisioned that the streams may exit at any desired output to achieve the desired heat exchange. The split partially-warmed nitrogen streams 241, 251 are then combined to a single partially-warmed nitrogen stream 207, and passed through a turboexpander 233 coupled to a brake 234. In passing through the turboexpander, the single warm nitrogen stream 207 is cooled, and the pressure decreases, thereby also increasing the amount of liquid in the stream, e.g., from about 0% in stream 207 to about 6% to about 10% in stream 208. A valve 235 is shown between the turboexpander 233 and first heat exchanger 231 which decreases the temperature and pressure of the cold nitrogen stream 208 before it is routed back to, and for a second pass through, the first heat exchanger. With passage through the first heat exchanger 231, the cold, low-pressure nitrogen stream 209 is warmed. In passing through the first heat exchanger 231, the liquid in cold, low-pressure nitrogen stream 209 is vaporized such that partially-warmed nitrogen gas stream 210 is about 0% liquid. The partially-warmed nitrogen gas stream is then directed through the second heat exchanger 230 wherein the partially-warmed nitrogen gas stream 210 is warmed and a warm hydrogen or helium gas stream 201 is cooled to provide a fully-warmed nitrogen gas stream 211 and the partially-cooled hydrogen or helium gas stream 202. It may be understood that while it may appear from the figures that the partially-warmed nitrogen gas stream 210 leaves the first heat exchanger 231 to then enter the second heat exchanger 230, when the first heat exchanger and the second heat exchanger are two parts of a single unit, the stream flows from the first heat exchanger directly to the second heat exchanger, while remaining within the single heat exchanger unit. The second heat exchanger 230 may include auxiliary refrigeration, such as propene streams 214, 215. Liquid propene stream 214 passes through the second heat exchanger 230 which exchanges heat between the auxiliary refrigeration and the warm hydrogen or helium gas stream 201, such that liquid propene stream 214 passes through the second heat exchanger and exits as a gas propene stream 215. Table 2 includes a listing of the streams and equipment shown in FIG. 2 and the properties for each of the streams. The liquid nitrogen consumption, calculated by dividing the LIN supply flow rate by precooled hydrogen flow rate (i.e., the flow rate of stream 204/203) is 5.18 kg LIN/kg LH₂.

TABLE 2 FLOW Stream or RATE TEMP. PRESSURE LIQUID Equipment Number kg/hr COMPOSITION ° C. bar (a) % 201 625 H₂, 75% o, 25% p 29 38 0 202 625 H₂, 75% o, 25% p −42.2 37.8 0 203 625 H₂, 52.6% o, −191.1 37.58 0 47.4% p 204 3238 N₂ −192.6 1.45 100 250 2207 N₂ −189.5 32 100 240 1031 N₂ −189.5 32 100 241 2207 N₂ −43.6 31.9 0 251 1031 N₂ −172.0 31.9 0 207 3238 N₂ −118.4 31.9 0 208 3238 N₂ −187.2 2.5 7.44 209 3238 N₂ −192.6 1.45 4.43 210 3238 N₂ −43.6 1.35 0 211 3238 N₂ 26.9 1.25 0 212 HEAT EXCHANGER 213 HEAT EXCHANGER 214 915.3 PROPENE −43.6 1.25 100 215 915.3 PROPENE −43.61 1.20 0 216 TURBOEXPANDER 217 PUMP 234 BRAKE

FIG. 3 illustrates a process and system 300 for precooling hydrogen or helium gas using a liquid nitrogen stream and four turboexpander-compressors and auxiliary refrigeration supplied at −26° C. and −46° C. The system of FIG. 3 is configured so that the liquid nitrogen stream 304 is split and a portion of the liquid nitrogen supply is routed through pump 332 to provide a pressurized liquid nitrogen stream 306. The other portion of the liquid nitrogen supply 305 is routed through a valve 384 and then stream 325 passes into the first heat exchanger 331 where it is warmed to provide a first partially-warmed nitrogen gas stream 326 which is then passed through the second heat exchanger for further warming to provide a first fully-warmed nitrogen gas stream 327. The pressurized liquid nitrogen stream 306 also passes through the first heat exchanger 331, whereby the temperature of the pressurized liquid nitrogen stream 306 increases and the pressure remains substantially constant, e.g., any pressure differential may be less than about 1 bar. The second partially-warmed nitrogen gas stream 322 then passes through the second heat exchanger 330 for further warming, and exiting at a middle output, to provide a nitrogen gas stream 307, and passes through turboexpanders 333, 334, each of which is coupled to a compressor 335, 336, to provide nitrogen gas streams 308, 309. The turboexpanders may be designed to drive compressors, pumps, oil brakes or any other similar power-consuming device to remove energy from the system 300. In passing through the first turboexpander 333, the nitrogen gas stream 307 is cooled to a cold nitrogen gas stream 308. In passing through the second turboexpander 334, the cold nitrogen gas stream 308 is cooled to a cold, low-pressure nitrogen gas stream 309. Each turboexpander reduces the pressure of the nitrogen stream passing therethrough. There may optionally be a valve (not shown) between the second turboexpander and first heat exchanger to decrease the temperature and pressure of the cold, low-pressure nitrogen stream before it is routed back to and for a second pass through the first heat exchanger. After passage through the first heat exchanger 331, the third partially-warmed nitrogen gas stream 310 then passes through the second heat exchanger 330 wherein the third partially-warmed nitrogen gas stream 310 is warmed and a warm hydrogen gas stream 301 is cooled to provide a fully-warmed nitrogen gas stream 311 and the partially-cooled hydrogen gas stream 302. The second heat exchanger 330 may include auxiliary refrigeration, such as two auxiliary refrigeration systems, as shown including a first auxiliary refrigeration system including propene streams 350, 351, and a second auxiliary refrigeration system including propene streams 360, 361. In these auxiliary refrigeration systems, liquid propene streams 350, 360 pass through the second heat exchanger which exchanges heat between the propene stream and the warm hydrogen gas stream 301, such that liquid propene streams 350, 360 pass through the second heat exchanger and exit as gas propene streams 351, 361.

In FIG. 3, the fully-warmed nitrogen gas stream 311 is routed through four pairs of compressor 335, 336, 337, 338, followed by cooler 382, 383, 381, 380, and then routed through a third and a fourth turboexpander 339, 340. It will be envisioned that any number of pairs of compressor and cooler (e.g., between one pair and 6 pairs), followed by any number of turboexpanders (e.g., one to four) may be incorporated into the system. The compressor followed by the cooler removes the heat of compression by ambient air or cooling water or brine. After routing nitrogen stream 311 through the compressor, nitrogen stream 312 through the cooler, nitrogen stream 313 through the compressor, nitrogen stream 314 through the cooler, nitrogen stream 315 through the compressor, nitrogen stream 316 through the cooler, nitrogen stream 317 through the compressor, nitrogen stream 318 through the cooler, and nitrogen streams 319, 320 through the turboexpanders, the nitrogen gas stream 321 passes through the second heat exchanger 330 and a fully-warmed nitrogen gas stream 323 is combined with fully-warmed nitrogen gas stream 327 to make a combined fully-warmed nitrogen gas stream 324.

Table 3 includes a listing of the streams and equipment shown in FIG. 3 and the properties of each of the streams. The liquid nitrogen consumption, calculated by dividing the LIN supply flow rate by precooled hydrogen flow rate, is 4.30 kg LIN/kg LH₂

TABLE 3 Stream or FLOW RATE TEMP. PRESSURE LIQUID Equipment Number kg/hr COMPOSITION ° C. bar (a) % 301 1250 H₂, 75% o, 25% p 29 38 0 302 1250 H₂, 75% o, 25% p −131.0 37.8 0 303 1250 H₂, 52.6% o, −191.1 37.58 0 47.4% p 304 5380 N₂ −192.9 1.40 100 305 1280 N₂ −192.9 1.40 100 325 1280 N₂ −194.3 1.20 98.63 306 4100 N₂ −188.5 55.0 100 307 4100 N₂ −46.0 54.9 0 308 4100 N₂ −117.1 13.0 0 309 4100 N₂ −174.4 2.15 0 310 4100 N₂ −136.8 2.13 0 311 4100 N₂ 27.50 2.08 0 312 4100 N₂ 73.35 3.119 0 313 4100 N₂ 29.0 3.019 0 314 4100 N₂ 84.10 4.876 0 315 4100 N₂ 29.0 4.776 0 316 4100 N₂ 94.72 8.406 0 317 4100 N₂ 29.0 8.306 0 318 4100 N₂ 90.25 14.10 0 319 4100 N₂ 29.0 14.00 0 320 4100 N₂ −36.80 5.00 0 321 4100 N₂ −108.1 1.10 0 322 4100 N₂ −136.80 54.95 0 323 4100 N₂ 27.50 1.050 0 324 5380 N₂ 27.50 1.050 0 326 1280 N₂ −136.8 1.150 0 327 1280 N₂ 27.50 1.100 0 330 HEAT EXCHANGER 331 HEAT EXCHANGER 332 PUMP 333 TURBOEXPANDER 334 TURBOEXPANDER 335 COMPRESS OR 336 COMPRESS OR 337 COMPRESS OR 338 COMPRESS OR 339 TURBOEXPANDER 340 TURBOEXPANDER 350 1000 PROPENE −46.00 1.08 100 351 1000 PROPENE −46.42 1.00 0 360 380 PROPENE −26.00 2.433 100 361 380 PROPENE −26.22 2.413 0

FIG. 4 illustrates a process and system 400 for precooling hydrogen or helium gas using a liquid nitrogen stream where the system includes two turboexpander-compressor combinations for precooling without an auxiliary refrigeration unit. The system of FIG. 4 is configured so that the liquid nitrogen supply is split into two streams, with a first portion of the liquid nitrogen supply being routed through pump 432 to provide a pressurized liquid nitrogen stream 406. The other portion of the liquid nitrogen supply 405 is routed through the first heat exchanger 431 where it is warmed and vaporized to provide a first partially-warmed nitrogen gas stream 421, which then passes through the second heat exchanger for further warming to provide a first fully-warmed nitrogen gas stream 422. The pressurized liquid nitrogen stream 406 is split into two pressurized liquid nitrogen streams 409, 407, each of which passes through the first heat exchanger 431 and exiting at different outputs, whereby the temperature of the pressurized liquid nitrogen streams increases and the pressure remains substantially constant, e.g., any pressure differential may be less than about 1 bar(a), and then combine to a second partially-warmed nitrogen gas stream 411. The second partially-warmed nitrogen gas stream 411 then passes through the second heat exchanger 430 for further warming to provide a fully-warmed nitrogen gas stream 412. In this example, fully-warmed nitrogen gas stream 412 is routed through two pairs of compressor 434. 436, followed by cooler 481, 480, and then through turboexpanders 435, 433, each of which is coupled to one of the compressors 434, 436. It will be envisioned that any number of pairs of compressor and cooler (e.g., between one pair and 6 pairs), followed by any number of turboexpanders (e.g., one to four) may be incorporated into the system. After routing stream 412 through a compressor, stream 413 through a cooler, stream 414 through a compressor, stream 415 through a cooler, stream 416 through a turboexpander, and stream 417 through a turboexpander, the cold, low pressure nitrogen gas stream 418 passes through the first heat exchanger 431 to provide another partially-warmed nitrogen gas stream 419 and then through the second heat exchanger 430 to provide a fully-warmed nitrogen gas stream 420, which is combined with stream 422 to make a combined fully-warmed nitrogen gas stream 423.

Table 4 includes a listing of the streams and equipment shown in FIG. 4 and the properties for each of the streams. The liquid nitrogen consumption, calculated by dividing the LIN supply flow rate by precooled hydrogen flow rate, is 5.35 kg LIN/kg LH₂.

TABLE 4 Stream or FLOW RATE TEMP. PRESSURE LIQUID Equipment Number kg/hr COMPOSITION ° C. bar (a) % 401 1250 H₂, 75% o, 25% 29.00 38.00 0 P 402 1250 H₂, 75% o, 25% −40.00 37.80 0 P 403 1250 H₂, 52.6% o, −191.1 37.58 0 47.4% p 404 6690 N₂ −192.9 1.400 100 405 1200 N₂ −192.9 1.400 100 406 5490 N₂ −191.3 21.00 100 407 4490 N₂ −190.7 21.00 0 408 4490 N₂ −46.09 20.95 0 409 1000 N₂ −190.7 21.00 100 410 1000 N₂ −165.0 20.96 100 411 5490 N₂ −90.62 20.95 0 412 5490 N₂ 27.92 20.90 0 413 5490 N₂ 106.7 39.31 0 414 54.90 N₂ 29 39.21 0 415 5490 N₂ 113.1 76.61 0 416 5490 N₂ 29.00 76.51 0 417 5490 N₂ −62.46 17.50 0 418 5490 N₂ −160.6 1.20 0 419 5490 N₂ −46.09 1.150 420 5490 N₂ 27.92 1.10 0 421 1200 N₂ −46.09 1.370 0 422 1200 N₂ 27.92 1.340 0 423 6690 N₂ 27.91 1.100 0 450 PUMP 451 HEAT EXCHANGER 452 HEAT EXCHANGER 453 TURBO EXPANDER 454 COMPRESSOR 455 TURBO EXPANDER 456 COMPRESSOR

A conventional precooling process is shown in FIG. 5 and described above. Table 5 includes a listing of the streams and equipment shown in FIG. 5 and the properties of each of the streams. By dividing the flow of liquid nitrogen stream 504 by the flow of precooled hydrogen stream 503, the liquid nitrogen requirement is 7.28 kg of liquid nitrogen per kg of hydrogen feed (7.28 kg LIN/kg LH₂), where the hydrogen also undergoes ortho-para conversion.

TABLE 5 Stream or Equipment FLOW RATE TEMPERATURE PRESSURE LIQUID Number kg/hr COMPOSITION ° C. bar (a) % 501 625 H₂, 75% o, 25% 29.00 38.00 0 P 503 625 H₂, 52.6% o, −191.1 37.58 0 47.4% p 504 4550 N₂ −192.9 1.400 99.6 505 4550 N₂ 27.50 1.200 0 502 HEAT EXCHANGER

While there have been described what are presently believed to be various aspects and certain desirable embodiments of the disclosure, those skilled in the art will recognize that changes and modifications may be made thereto without departing from the spirit of the disclosure, and it is intended to include all such changes and modifications as fall within the true scope of the disclosure. 

What is claimed:
 1. A method for precooling hydrogen or helium gas using a liquid nitrogen stream, the method comprising: a. providing a pressurized liquid nitrogen stream containing liquid nitrogen at a pressure between about 15 bar(a) and about 70 bar(a); b. passing the pressurized liquid nitrogen stream and a partially-cooled hydrogen or helium gas stream through a first heat exchanger that exchanges heat between the pressurized liquid nitrogen stream and the partially-cooled hydrogen or helium gas stream to provide a first partially-warmed nitrogen stream and a precooled hydrogen or helium gas stream; c. passing the first partially-warmed nitrogen stream through one or more turboexpanders that lowers the temperature and pressure of the partially-warmed nitrogen stream to provide a cold nitrogen stream; and d. passing the cold nitrogen stream through the first heat exchanger and through a second heat exchanger to provide the precooled hydrogen or helium gas stream, and a fully-warmed nitrogen gas stream.
 2. The method of claim 1, wherein step (d) comprises: passing the cold nitrogen stream through the first heat exchanger that exchanges heat between the cold nitrogen stream and the partially-cooled hydrogen or helium gas stream to provide a second partially-warmed nitrogen gas stream and the precooled hydrogen or helium gas stream; and passing the second partially-warmed nitrogen gas stream through the second heat exchanger that exchanges heat between the second partially-warmed nitrogen gas stream and a warm hydrogen or helium gas stream to provide a fully-warmed nitrogen gas stream and the partially-cooled hydrogen or helium gas stream.
 3. The method of claim 2, wherein the first heat exchanger and the second heat exchanger are separate devices.
 4. The method of claim 1, wherein the first heat exchanger and the second heat exchanger are parts within a single heat exchanger.
 5. The method of claim 1, wherein the pressurized liquid nitrogen has a pressure between about 15 bar(a) and about 70 bar(a).
 6. The method of claim 1, wherein the pressurized liquid nitrogen has a pressure between about 20 bar(a) and about 55 bar(a).
 7. The method of claim 1, wherein step (a) includes the steps of: supplying a liquid nitrogen stream produced at a saturation pressure of less than about 10 bar(a); followed by increasing the pressure of the liquid nitrogen stream to provide the pressurized liquid nitrogen stream.
 8. The method of claim 1, wherein step (a) includes the steps of: supplying a liquid nitrogen stream produced at a saturation pressure of less than about 10 bar(a); splitting the liquid nitrogen stream into a first portion of the liquid nitrogen stream and a second portion of the liquid nitrogen stream; and increasing a pressure of the first portion of the liquid nitrogen stream to provide the pressurized liquid nitrogen stream.
 9. The method of claim 8, further comprising passing the second portion of the liquid nitrogen stream through the first heat exchanger to provide a third partially-warmed nitrogen stream
 10. The method of claim 9, further comprising directing the third partially-warmed nitrogen stream through the second heat exchanger to provide a second fully-warmed nitrogen gas stream.
 11. The method of claim 1, further comprising applying an auxiliary refrigeration system coupled to the second heat exchanger.
 12. The method of claim 2, wherein the pressurized liquid nitrogen stream is split into a first pressurized liquid nitrogen stream and a second pressurized liquid nitrogen stream, and wherein the first pressurized liquid nitrogen stream and the second pressurized liquid nitrogen stream are passed separately through the first heat exchanger to exchange heat between the first and the second pressurized liquid nitrogen streams and the partially-cooled hydrogen or helium gas stream.
 13. The method of claim 1, wherein step (c) includes passing the first partially-warmed nitrogen stream through one or two turboexpanders.
 14. The method of claim 1, wherein step (c) includes passing the first partially-warmed nitrogen stream through one or more compressors before passing through the one or more turboexpanders.
 15. The method of claim 2, further comprising applying an auxiliary refrigeration system coupled to the second heat exchanger.
 16. A method for precooling hydrogen or helium gas using a liquid nitrogen stream, the method comprising: a. supplying a liquid nitrogen stream produced at a saturation pressure of less than about 10 bar(a); b. directing a first portion of the liquid nitrogen stream to a first heat exchanger to provide a first partially-warmed nitrogen stream; c. directing the first partially-warmed nitrogen stream to a second heat exchanger to provide a first fully-warmed nitrogen gas stream; d. increasing a pressure of a second portion of the liquid nitrogen stream to provide a pressurized liquid nitrogen stream at a pressure between about 15 bar(a) and about 70 bar(a); e. passing the pressurized liquid nitrogen stream and a partially-cooled hydrogen or helium gas stream through the first heat exchanger in countercurrent to provide a second partially-warmed nitrogen gas stream and a precooled hydrogen or helium gas stream; f. passing the second partially-warmed nitrogen gas stream through the second heat exchanger that exchanges heat between the second partially-warmed nitrogen gas stream and a warm hydrogen or helium gas stream to provide a second fully-warmed nitrogen gas stream and the partially-cooled hydrogen or helium gas stream; g. passing the second fully-warmed nitrogen gas stream through one or more turboexpanders that lower the temperature and pressure of the second fully-warmed nitrogen gas stream to provide a cold nitrogen stream; h. passing the cold nitrogen stream through the first heat exchanger that exchanges heat between the cold nitrogen stream and the partially-cooled hydrogen or helium gas stream to provide a third partially-warmed nitrogen gas stream and the precooled hydrogen or helium gas stream; and i. passing the third partially-warmed nitrogen gas stream through the second heat exchanger that exchanges heat between the third partially-warmed nitrogen gas stream and a warm hydrogen or helium gas stream to provide a third fully-warmed warm nitrogen gas stream and the partially-cooled hydrogen or helium gas stream.
 17. The method of claim 16, wherein step (g) comprises: routing the second fully-warmed nitrogen stream through one or more compressors and one or more coolers before passing the second fully-warmed nitrogen stream through the one or more turboexpanders.
 18. The method of claim 16, wherein step (g) includes passing the second fully-warmed nitrogen stream through two turboexpanders connected in series.
 19. The method of claim 16, wherein the pressurized liquid nitrogen stream is split into a first pressurized liquid nitrogen stream and a second pressurized liquid nitrogen stream; and wherein the first pressurized liquid nitrogen stream and the second pressurized liquid nitrogen stream are routed separately through the first heat exchanger.
 20. The method of claim 16, wherein the first heat exchanger and the second heat exchanger are separate devices.
 21. The method of claim 16, wherein the first heat exchanger and the second heat exchanger are parts within a single heat exchanger.
 22. The method of claim 16, further comprising applying an auxiliary refrigeration system coupled to the second heat exchanger.
 23. The method of claim 16, further including a system of recooling the second or third fully-warmed nitrogen gas stream, the system of recooling comprising: i. passing the second or third fully-warmed nitrogen gas stream through a first compressor and a first cooler to obtain a compressed and cooled nitrogen gas stream, wherein the first compressor is coupled to the second heat exchanger and to the first cooler; and ii. passing the compressed and cooled nitrogen gas stream through one or more turboexpanders; and iii. passing the turboexpanded nitrogen gas stream through the second heat exchanger to provide a fourth fully-warmed nitrogen gas stream.
 24. The method of claim 23, wherein step (ii) includes passing the compressed and cooled nitrogen gas stream through two turboexpanders connected in series.
 25. A precooling system using liquid nitrogen for hydrogen or helium liquefaction, the system comprising: a warm hydrogen or helium gas stream; a pressurized liquefied nitrogen stream from a supply of liquefied nitrogen; a heat exchanger configured to exchange heat between the pressurized liquefied nitrogen stream and a warm hydrogen or helium gas stream to increase a temperature of the pressurized liquefied nitrogen stream to provide a warm nitrogen gas stream, and decrease a temperature of the warm hydrogen or helium gas stream to provide a precooled nitrogen gas stream; and at least one turboexpander coupled to the heat exchanger and configured to lower a temperature of a partially-warmed nitrogen gas stream discharged from the heat exchanger.
 26. The precooling system of claim 25, further comprising at least one compressor and at least one cooler configured to receive the warm nitrogen gas stream discharged from the heat exchanger.
 27. The precooling system of claim 26, further comprising at least one turboexpander configured to receive the warm nitrogen gas stream after passage through the at least one compressor and the at least one cooler.
 28. The precooling system of claim 26, further comprises a valve coupled to the turboexpander configured to reduce the pressure of the nitrogen gas stream.
 29. A precooling system using liquid nitrogen for hydrogen or helium liquefaction, the system comprising: a warm hydrogen gas stream or helium gas stream; a pressurized liquefied nitrogen stream from a supply of liquefied nitrogen; a first heat exchanger configured to exchange heat between the pressurized liquefied nitrogen stream and a partially-cooled hydrogen or helium gas stream to increase a temperature of the pressurized liquefied nitrogen stream to provide a partially-warmed nitrogen gas stream, and decrease a temperature of the partially-cooled hydrogen or helium gas stream; at least one turboexpander configured to lower the temperature of the partially-warmed nitrogen gas stream; and a second heat exchanger configured to exchange heat between the partially-warmed nitrogen gas stream and the warm hydrogen or helium gas stream to increase a temperature of the partially-warmed nitrogen gas stream to provide a fully-warmed nitrogen gas stream, and to decrease a temperature of the warm hydrogen or helium gas stream.
 30. The precooling system of claim 29, further comprising at least one compressor and at least one cooler configured to receive the fully-warmed nitrogen gas stream after passage through the second heat exchanger. 